The present invention relates to anti-piracy systems for discouraging and/or preventing theft of items such as electronic representations, particularly electronic video representations.
Anti-piracy methods and apparatus for discouraging and/or preventing theft of items such as electronic representations are well known in the art. Prominent among the methods is a class of methods known collectively as watermarking. In watermarking methods, a watermark signal is typically added to an electronic representation to be protected. In such methods the added signal typically carries information identifying the owner of the electronic representation, and may carry additional information such as an identification of a buyer of a copy of the electronic representation. The added signal is, in some case, visible but in many cases the added signal is disguised so that a potential thief or pirate could find the signal only with great difficulty. Another preferred attribute of watermarking methods is that alterations of the picture, such as adding noise, not erase the watermark.
Typical watermarking methods are described in the following:
Digimarc(copyright) Watermarking Guide, 1997, Digimarc Corporation, 521 SW 11th Ave., Suite 200, Portland, OR 97205;
Project DigiLock, The Digital Content Protection Solution for Copy Control and Play Control, presented by Macrovision Corporation and Digimarc Corporation, Fall, 1997;
European Patent Application EP 0 651 554 A1, assigned to Eastman Kodak Company;
PCT Patent Application WO 96/41468, assigned to Macrovision Corporation;
PCT Patent Application WO 97/13248, assigned to Philips Electronics N.V.;
PCT Patent Application WO 97/22206, assigned to Philips Electronics N.V.;
PCT Patent Application 97/26732, assigned to The Dice Company;
PCT Patent Application 97/26733, assigned to The Dice Company;
PCT Patent Application 97/34391, assigned to Leighton;
PCT Patent Application 98/02864, assigned to The Dice Company;
PCT Patent Application 98/03014, assigned to Philips Electronics N.V.;
U.S. Pat. No. 5,606,609 to Houser et al;
U.S. Pat. No. 5,607,188 to Bahns et al;
U.S. Pat. No. 5,636,292 to Rhoads;
U.S. Pat. No. 5,659,726 to Sandford, II et al;
U.S. Pat. No. 5,664.018 to Leighton; and
U.S. Pat. No. 5,687,236 to Moskowitz et al;
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.
The present invention seeks to provide an improved anti-piracy system. In the present invention a video representation, including a plurality of frames, is assigned a signature, typically a signature based on frame characteristic values which represent characteristics visible to a viewer of the video representation. Thus, an attempt to alter the video representation in order to alter the signature such an attempt typically being analogous to well-known methods of altering a video representation in order to obliterate a watermark would alter the visible characteristics of the video representation.
A particular method of computing such a signature, based on selecting a plurality of frames and dividing each frame into a plurality of regions, is also provided. In this method, a particular region is chosen from each frame and some characteristic, such as average pixel value in the region, is used to characterize the frame. A signature is then computed based on the plurality, of characterizing values from the plurality of frames.
Preferably, the signature is transmitted to playing devices which will then reject, by refusing to play, any recording having the transmitted signature. Typically, the playing device will attempt to match a computed signature of a recording with the transmitted signature.
The term xe2x80x9cmatchxe2x80x9d, as used throughout the present specification and claims in referring to comparison of signatures or a result of such comparison, is used in a broad sense to include not only a determination that two signatures are identical but also any analogous determination, using any appropriate signature mechanism, which establishes that the two signatures represent two acts of signing identical material. It is appreciated that there may be appropriate signature mechanisms for which two such matching signatures are not actually identical. For example and without limiting the generality of the foregoing in some signature methods based on public/private key systems, which are well known in the art, two such matching signatures may not be actually identical.
It is appreciated that the system of the present invention is particularly applicable in a case where all playing devices are built to conform to the system. It is also appreciated that the system of the present invention is particularly applicable to preventing the distribution of pirate copies of video material which has no legitimate distribution channel. One example of such video material is a master copy of an as-yet unreleased movie.
Although the present invention relates especially to video representations it is appreciated that similar methods could be applied in the case of other electronic representations such as audio representations.
There is thus provided in accordance with a preferred embodiment of the present invention a method for assigning a signature to a video representation, the video representation including a plurality of frames, the method including choosing a chosen plurality of frames from among the plurality of frames included in the video representation, for each of the chosen plurality of frames, computing a frame characteristic value, thus producing a plurality of frame characteristic values, and computing a function of the plurality of frame characteristic values and assigning a result of the function as the signature.
Further in accordance with a preferred embodiment of the present invention the function includes concatenation of the plurality of frame characteristic values.
Still further in accordance with a preferred embodiment of the present invention the video representation includes an MPEG representation, and each of the chosen plurality of frames includes an I-frame.
Additionally in accordance with a preferred embodiment of the present invention the method also includes communicating the signature to a playing device.
Moreover in accordance with a preferred embodiment of the present invention the method also includes providing a recorded video representation to the playing device, computing a signature of the recorded video representation, and preventing playback of the video representation in the playing device if the computed signature of the recorded video representation matches the signature communicated to the playing device.
Further in accordance with a preferred embodiment of the present invention the step of preventing playback includes preventing playback of the video representation in the playing device if the computed signature of the recorded video representation is identical to the signature communicated to the playing device.
Still further in accordance with a preferred embodiment of the present invention the step of preventing playback includes employing a signature comparison method to determine whether the computed signature of the recorded video representation matches the signature communicated to the playing device wherein the signature comparison method includes determining that a first signature and a second signature match even if the first signature is not identical to the second signature.
Additionally in accordance with a preferred embodiment of the present invention the step of computing a frame characteristic value includes dividing the frame into a plurality of regions, choosing one of the plurality of regions, and computing a region characteristic value of the chosen region and assigning the region characteristic value as the frame characteristic value.
Moreover in accordance with a preferred embodiment of the present invention the region characteristic value includes a function of average pixel value for the region.
Further in accordance with a preferred embodiment of the present invention the function of average pixel value produces a 1-bit value.
Still further in accordance with a preferred embodiment of the present invention the function of average pixel value produces a 1-bit value of xe2x80x9c1xe2x80x9d for a first one of the chosen plurality of frames.
Additionally in accordance with a preferred embodiment of the present invention the step of dividing the frame into a plurality of regions includes, for each frame in the chosen plurality of frames, dividing the frame into a plurality of regions each corresponding to one of the plurality of regions into which every other frame of the chosen plurality of frames is divided.
Moreover in accordance with a preferred embodiment of the present invention the step of choosing one of the plurality of regions includes choosing, for each frame in the chosen plurality of frames, a region corresponding to the region chosen in ever, other frame of the chosen plurality of frames.
Further in accordance with a preferred embodiment of the present invention the step of choosing one of the plurality of regions includes choosing, for at least one frame in the chosen plurality of frames a region not corresponding to a region chosen in at least one other frame of the chosen plurality of frames.
There is also provided in accordance with another preferred embodiment of the present invention an anti-piracy method including computing a forbidden signature of a forbidden video representation, communicating the forbidden signature to a playing device, providing a recorded video representation to the playing device, computing a signature of the recorded video representation and preventing playback of the recorded video representation in the playing device if the computed signature of the recorded video representation matches the forbidden signature communicated to the playing device.
Further in accordance with a preferred embodiment of the present invention the method also includes storing the forbidden signature at the playing device, and retrieving the forbidden signature before performing the preventing playback step.
There is also provided in accordance with another preferred embodiment of the present invention a system for assigning a signature to a video representation, the video representation including a plurality of frames, the system including frame selection apparatus for choosing a chosen plurality of frames from among the plurality of frames included in the video representation, a frame characteristic determination unit operative, for each of the chosen plurality of frames, to compute a frame characteristic value, thus producing a plurality of frame characteristic values, and signature apparatus for computing a function of the plurality of frame characteristic values and assigning a result of the function as the signature.
There is also provided in accordance with another preferred embodiment of the present invention an anti-piracy system including video representation signature apparatus for computing a forbidden signature of a forbidden video representation, communication apparatus for communicating the forbidden signature to a playing device, and a playing device adapted to receive and play back a recorded video representation, the playing device including reception apparatus for receiving the forbidden signature communicated by the communication apparatus, recorded video representation signature apparatus for computing a signature of the recorded video representation and playback control apparatus operative to prevent playback of the recorded video representation if the computed signature of the recorded video representation matches the forbidden signature communicated to the playing device.
Further in accordance with a preferred embodiment of the present invention the reception apparatus is operative to receive the forbidden signature during playback of a non-forbidden recorded video representation.
Still further in accordance with a preferred embodiment of the present invention the reception apparatus is also operative to receive an authorization message authorizing playback of the non-forbidden recorded video representation, and the authorization message includes the forbidden signature.
There is also provided in accordance with another preferred embodiment of the present invention a playing device adapted to receive and play back a recorded video representation, the playing device including reception apparatus for receiving a forbidden signature of a forbidden video representation, recorded video representation signature apparatus for computing a signature of the recorded video representation, and playback control apparatus operative to prevent playback of the recorded video representation if the computed signature of the recorded video representation matches the forbidden signature received by the playing device.
Further in accordance with a preferred embodiment of the present invention the playing device also includes forbidden signature storage apparatus operative to store the forbidden signature, and wherein the playback control apparatus receives the forbidden signature from the forbidden signature storage apparatus.